1. Field of the Invention
The present invention is in the field of filling apparatus for filling receviers with granular material and more particularly in the field of apparatus for filling charcoal adsorber filters with granular charcoal. Specifically, the present invention relates to an apparatus for filling a granular charcoal filter adsorber apparatus with granular charcol, from above the apparatus, in such a fashion as to achieve a substantially uniform packing density of granular charcoal within the adsorber apparatus. The present invention also relates to a method for filling the fill apparatus with the granular charcoal which will minimize the time involved for this procedure. The present apparatus is most specifically designed to be used in conjunction with vertically oriented planar charcoal adsorber filter cells to achieve a uniform packing density of charcoal within such cells, thereby avoiding channeling effects when air is passed through the cells.
2. Description of the Prior Art
Apparatus for dispensing granular materials and for filling containers with granular materials have long been known and a variety of such apparatus has been used to perform the these tasks. Typical of these devices are the apparatus shown in U.S. Pat. No. 117,718, U.S. Pat. No. 335,709 and U.S. Pat. No. 2,511,089.
With evolving technology, the need has arisen for more sophisticated apparatus and specifically for apparatus to obtain a more sophisticated result, that being to achieve packing of the granular material in a substantially uniform fashion within a hopper, filter or other structure which is to be filled with granular materia. This requirement is particularly acute in air filter systems using granular charcoal adsorbers for filtering radioactive materials out of the air in the case of an accident at a nucler power plant.
The U.S. Nuclear Regulatory Commission has issued Regulatory Guides which set forth general design criteria for the design of nuclear power plants and the allied equipment required thereby. One key system for the nuclear power plant is an atmospheric clean-up system for which general design guidelines are given in NRC Regulatory Guide 1.52. As an integral part of the atmospheric clean-up system, at least one adsorption unit is required for adsorbing radioactive materials from the air in the case of an accident. These adsorption units are manufactured in a variety of design configurations, two of which are described in U.S. PAT. Nos. 3,925,046 and 3,964,890. These charcoal adsorber units require that the charcoal adsorbent be filled in the adsorber unit from above the unit and that the filling result in a substantially uniform density of the charcoal adsorbent within the adsorber unit. This substantially uniform density prevents so called "channeling" whereby paths of low resistance are available for air passing through the adsorber unit. Such channeling is undesirable since air, to be properly filtered while passing through the adsorber, must spend a sufficient time in residence in the adsorber cells which are filled with charcoal so that radioactive wastes in the air can be adsorbed by the charcoal. Cells with channeling effects present do not achieve satisfactory residence time for the air passing through them; consequently, the air is not sufficiently purified and radioactive contaminants may remain in the air emerging from the adsorber.
In the past, it has been thought that by vibrating an adsorber unit, once it is filled with the granular charcoal, settling of the charcoal would occur thereby minimizing channeling effects. In fact, vibration of a filled cell of the adsorber apparatus may result in aggravating the channeling problem due to vibrational nodes in the cell structure with consequent non-uniform vibration of the adsorber unit and the charcoal therein.
Experiments have shown that the present invention not only provides a uniform packing density of charcoal adsorbent when utilized to fill a charcoal adsorber cell, but also achieves a greater packing density than is achieved by vibrating the cell. Such greater packing density enhances performance of the cell and has a further advantage in that by increasing flow resistance through the adsorber cell, the degree of low channeling, due to possible entrance and exit effects where the air enters and leaves the cell, is also decreased. Most importantly, the apparatus produces a very uniform packing of a charcoal adsorber cell and this results in a uniform flow resistance to air passing through the adsorber cell.